example_erc20_gas/
handler.rs

1use revm::{
2    context::Cfg,
3    context_interface::{
4        result::{HaltReason, InvalidTransaction},
5        Block, ContextTr, JournalTr, Transaction,
6    },
7    handler::{
8        pre_execution::validate_account_nonce_and_code, EvmTr, EvmTrError, FrameResult, FrameTr,
9        Handler,
10    },
11    interpreter::interpreter_action::FrameInit,
12    primitives::{hardfork::SpecId, U256},
13    state::EvmState,
14};
15
16use crate::{erc_address_storage, token_operation, TOKEN, TREASURY};
17
18/// Custom handler that implements ERC20 token gas payment.
19/// Instead of paying gas in ETH, transactions pay gas using ERC20 tokens.
20/// The tokens are transferred from the transaction sender to a treasury address.
21#[derive(Debug)]
22pub struct Erc20MainnetHandler<EVM, ERROR, FRAME> {
23    _phantom: core::marker::PhantomData<(EVM, ERROR, FRAME)>,
24}
25
26impl<CTX, ERROR, FRAME> Erc20MainnetHandler<CTX, ERROR, FRAME> {
27    /// Creates a new ERC20 gas payment handler
28    pub fn new() -> Self {
29        Self {
30            _phantom: core::marker::PhantomData,
31        }
32    }
33}
34
35impl<EVM, ERROR, FRAME> Default for Erc20MainnetHandler<EVM, ERROR, FRAME> {
36    fn default() -> Self {
37        Self::new()
38    }
39}
40
41impl<EVM, ERROR, FRAME> Handler for Erc20MainnetHandler<EVM, ERROR, FRAME>
42where
43    EVM: EvmTr<Context: ContextTr<Journal: JournalTr<State = EvmState>>, Frame = FRAME>,
44    FRAME: FrameTr<FrameResult = FrameResult, FrameInit = FrameInit>,
45    ERROR: EvmTrError<EVM>,
46{
47    type Evm = EVM;
48    type Error = ERROR;
49    type HaltReason = HaltReason;
50
51    fn validate_against_state_and_deduct_caller(&self, evm: &mut Self::Evm) -> Result<(), ERROR> {
52        let context = evm.ctx();
53        let basefee = context.block().basefee() as u128;
54        let blob_price = context.block().blob_gasprice().unwrap_or_default();
55        let is_balance_check_disabled = context.cfg().is_balance_check_disabled();
56        let is_eip3607_disabled = context.cfg().is_eip3607_disabled();
57        let is_nonce_check_disabled = context.cfg().is_nonce_check_disabled();
58        let caller = context.tx().caller();
59        let value = context.tx().value();
60
61        let (tx, journal) = context.tx_journal_mut();
62
63        // Load caller's account.
64        let caller_account = journal.load_account_code(tx.caller())?.data;
65
66        validate_account_nonce_and_code(
67            &mut caller_account.info,
68            tx.nonce(),
69            is_eip3607_disabled,
70            is_nonce_check_disabled,
71        )?;
72
73        if tx.kind().is_call() {
74            caller_account.info.nonce = caller_account.info.nonce.saturating_add(1);
75        }
76
77        // Touch account so we know it is changed.
78        caller_account.mark_touch();
79
80        let max_balance_spending = tx.max_balance_spending()?;
81        let effective_balance_spending = tx
82            .effective_balance_spending(basefee, blob_price)
83            .expect("effective balance is always smaller than max balance so it can't overflow");
84
85        let account_balance_slot = erc_address_storage(tx.caller());
86        context.journal_mut().load_account(TOKEN)?.data.mark_touch();
87
88        let account_balance = context
89            .journal_mut()
90            .sload(TOKEN, account_balance_slot)
91            .map(|v| v.data)
92            .unwrap_or_default();
93
94        if account_balance < max_balance_spending && !is_balance_check_disabled {
95            return Err(InvalidTransaction::LackOfFundForMaxFee {
96                fee: Box::new(max_balance_spending),
97                balance: Box::new(account_balance),
98            }
99            .into());
100        };
101
102        // Check if account has enough balance for `gas_limit * max_fee`` and value transfer.
103        // Transfer will be done inside `*_inner` functions.
104        if is_balance_check_disabled {
105            // ignore balance check.
106        } else if max_balance_spending > account_balance {
107            return Err(InvalidTransaction::LackOfFundForMaxFee {
108                fee: Box::new(max_balance_spending),
109                balance: Box::new(account_balance),
110            }
111            .into());
112        } else {
113            // subtracting max balance spending with value that is going to be deducted later in the call.
114            let gas_balance_spending = effective_balance_spending - value;
115
116            token_operation::<EVM::Context, ERROR>(
117                context,
118                caller,
119                TREASURY,
120                gas_balance_spending,
121            )?;
122        }
123
124        Ok(())
125    }
126
127    fn reimburse_caller(
128        &self,
129        evm: &mut Self::Evm,
130        exec_result: &mut <<Self::Evm as EvmTr>::Frame as FrameTr>::FrameResult,
131    ) -> Result<(), Self::Error> {
132        let context = evm.ctx();
133        let basefee = context.block().basefee() as u128;
134        let caller = context.tx().caller();
135        let effective_gas_price = context.tx().effective_gas_price(basefee);
136        let gas = exec_result.gas();
137
138        let reimbursement =
139            effective_gas_price.saturating_mul((gas.remaining() + gas.refunded() as u64) as u128);
140
141        token_operation::<EVM::Context, ERROR>(
142            context,
143            TREASURY,
144            caller,
145            U256::from(reimbursement),
146        )?;
147
148        Ok(())
149    }
150
151    fn reward_beneficiary(
152        &self,
153        evm: &mut Self::Evm,
154        exec_result: &mut <<Self::Evm as EvmTr>::Frame as FrameTr>::FrameResult,
155    ) -> Result<(), Self::Error> {
156        let context = evm.ctx();
157        let tx = context.tx();
158        let beneficiary = context.block().beneficiary();
159        let basefee = context.block().basefee() as u128;
160        let effective_gas_price = tx.effective_gas_price(basefee);
161        let gas = exec_result.gas();
162
163        let coinbase_gas_price = if context.cfg().spec().into().is_enabled_in(SpecId::LONDON) {
164            effective_gas_price.saturating_sub(basefee)
165        } else {
166            effective_gas_price
167        };
168
169        let reward = coinbase_gas_price.saturating_mul(gas.used() as u128);
170        token_operation::<EVM::Context, ERROR>(context, TREASURY, beneficiary, U256::from(reward))?;
171
172        Ok(())
173    }
174}
example_erc20_gas/handler.rs

example_erc20_gas/
handler.rs
